Back pressure sensitive switch for a flueric device

ABSTRACT

A back pressure sensitive fluidic switching mechanism is disclosed. A fluidic device incorporating this mechanism will switch from one output receiver channel to another under the effect of back pressure produced by a control signal issuing from a control port disposed at, in, or near the output channel of the device. Decoupling vents are provided downstream of the control ports in each output receiver channel so as to insulate the device from the effects of load impedance. Operational stability may be achieved by the provision of side vents in conjunction with each control port such that the control signal, when applied, serves to block the vent.

United States Patent [191 Trask, II

[4 1 May22,1973

[54] BACK PRESSURE SENSITIVE SWITCH [73] Assignee: The United States of America as represented by the Secretary oi the Army, Washington, DC.

[22] Filed: Sept. 1, 1971 [21] Appl.No.: 177,033

3,413,994 12/1968 Sowers ..l37/81.5 3,420,253 1/1969 Griffin..... ..137/81.5 3,428,065 2/1969 Cawley.... ..l37/8l.5 3,444,879 5/1969 McLeod ..l37/81.5

Primary Examiner-Samuel Scott Attorney-l-1arry M. Saragovitz et a1.

[57] ABSTRACT A back pressure sensitive fluidic switching mechanism is disclosed. A fluidic device incorporating this mechanism will switch from one output receiver channel to another under the effect of back pressure produced by a control signal issuing from a control port disposed at, in, or near the output channel of the device. Decoupling vents are provided downstream of the control ports in each output receiver channel so as to insulate the device from the effects of load impedance. Operational stability may be achieved by the provision of side vents in conjunction with each control port such that the control signal, when applied, serves to block the vent.

5 Claims, 3 Drawing Figures PATENTEDHAYZZ ma NVENT ROLAND PIE E T BY M4041;

ATTORNEYS BACK PRESSURE SENSITIVE SWITCH FOR A FLUERIC DEVICE The invention described herein may be manufactured, used, and licensed by or for the United States Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION This invention generally relates to fluidic devices and particularly concerns a fluidic device constructed so as to achieve back pressure switching.

Conventional fluidic devices such as fluid amplifiers typically operate in accordance with boundary layer control principles wherein the power stream issuing from an input channel into an interaction chamber is directed to a particular outlet channel communicating with the interaction chamber by means of pressure distributions occurring in the interaction chamber and affecting the power stream. The particular pressure distribution achieved within the interaction chamber is determined by a number of factors including interaction chamber geometry, flow parameters, and back pressure loading of the device and, in the typical construction of such prior fluid amplifiers, deflection or exit of the power stream into one of a plurality of output receiver channels provided takes place under the influence of a control port communicating with the interaction chamber in such a way that signals from the control port alter the pressure distribution in a selective manner.

Typically, with such constructions, back pressure created within the interaction chamber by load conditions, for example, oftentimes effects a spurious switching of amplifiers of the general type above-described causing the fluidic circuits in which such devices are utilized to assume an erroneous state. So as to eliminate or at least substantially reduce the effect of such back pressure, prior art fluidic amplifier devices utilized vents in an effort to make such devices more or less insensitive to load conditions and thus operate in a more stable fashion under the influence of the control ports alone.

SUMMARY OF THE INVENTION Departing from prior art constructions and approaches, the instant invention contemplates the provi sion of a fluidic device which is specifically constructed to be back pressure sensitive so as to effect switching of the power stream from one output receiver channel to another by means of back pressure.

A further objective of the instant invention concerns the provision of such a back pressure sensitive switching device wherein back pressure switching is effected under the influence of a control signal rather than under the influence of changing output load conditions.

A still further objective of the instant invention concerns the provision of such a fluidic back pressure switching device wherein no control ports are utilized in the interaction chamber itself, this feature of the instant invention being particularly useful in conjunction with low power, and/or high gain amplifiers.

These objects as well as other which will become apparent as the description proceeds are implemented by the instant back pressure sensitive fluidic switching device, which device incorporates the typical input channel means for issuing a fluidic power stream, a plurality of output receiver channels for receiving at least a portion of the power stream fiow, and an interaction chamber means disposed between the input channel means and the output receiver channel means, the interaction chamber including side walls to which the power stream attaches so as to exit into an output receiver channel.

Rather than providing control ports at or in the interaction chamber itself, the instant invention proposes to provide control port means which communicate with the fluid in or near the output receiver channel, a control signal being applied to the control port means so as to increase the back pressure within the interaction chamber and/or the impedance of the output receiver channel to which or near which the control signal is applied. Such increase in back pressure serves to selectively switch the power stream in the interaction cham ber means to another output receiver channel having a relatively lower impedance. Since switching of the novel device is contemplated to take place only upon application of control signals to the novel control port means, decoupling vents may be placed in the output receiver channels downstream of the control port means. In this fashion, sensitivity of the fluidic device of the instant invention to changes in load impedance is avoided. Additionally, and in the preferred inventive construction, each decoupling vent will be seen to include a decoupling nozzle disposed in the output receiver channel and, as will be more fully explained hereinbelow, the flow area of the decoupling nozzle serves to control and maintain substantially constant the output impedance of the receiver channel to thereby control the sensitivity of the device to the pressure control signal applied at the control port means.

In yet another preferred embodiment of the instant invention, side vent means are provided at the location of the control port means in the output receiver channels so as to achieve operational stability. In the preferred construction, these side vent means are disposed slightly downstream of the control port means in the output receiver channel and are oriented with respect to the control port means such that a control signal issuing from the control port means serves toblock the side vents.

In still another alternative though preferred inventive embodiment particularly designed for utilization as a low power, high gain device, the interaction chamber is itself constructed as a diffuser-type chamber having two opposite divergent side walls to as to effect a smooth, continuous, and gradual transition from the throat of the input channel to the output receiver channel. The provision of a control port in the output reciver channel itself so as to effect back pressure switching in accordance with the principles of the instant invention eliminates the need for disposing a control port in the area of the interaction region itself and thus assures low power and high gain operation.

BRIEF DESCRIPTION OF THE DRAWINGS The instant invention will be better understood and additional features and advantages thereof will become apparent from the following detailed description of preferred inventive embodiments, such description making reference to the appended sheet of drawings, wherein:

FIG. 1 is a schematic plan view of one embodiment of a novel device incoporating the instant back pressure sensitive fluidic switching mechanism;

FIG. 2 is a schematic plan view of a further embodiment of the invention exhibiting greater stability in operation; and

FIG. 3 is a schematic plan view of yet another preferred inventive embodiment exhibiting still greater operational stability.

Throughout the several figures of the drawings, like parts have been indicated by the same reference numerals.

DETAILED DESCRIPTION OF PREFERRED INVENTIVE EMBODIMENTS Referring initially to FIG. 1 of the appended drawings, a first embodiment of the novel back pressure sensitive fluidic switching device is disclosed. The device will be seen to include an input channel means having an orifice or power nozzle 12 for issuing a fluidic power stream into an interaction chamber means 14 having oppositely disposed side walls 16 and 18. A plurality of output receiver channel means and 22 are provided communicating with the interaction chamber means 14 for receiving at least a portion of the power of the power stream flow in a selective manner as will be described hereinbelow.

Since the novel device is contempated to effect a switching of the power stream from one output channel means 20 or 22, to the other output channel means upon the creation of a predetermined back pressure alone, control port means 36 and 38 are provided at, in, or near each output channel leg 20 and 22, respectively, communicating with the flow issuing into the respective output receiver channels. The placement of such control port means differs from the typical fluidic device construction wherein control ports are disposed in the region of the power nozzle in the interaction chamber.

During operation of the novel fluidic device as above-described, a power stream issues from the input channel means 10 and, in well-known fashion due to pressure differentials existing within the interaction chamber means 14, attaches to one or the other of the side walls 16 and 18 of the interaction chamber means 14 and subsequently exits via an output reciever channel 20 or 22, depending upon internal geometry of the interaction chamber means 14. Upon application of a control signal through one or the other of the control port means 36 or 38, which control signal increases the back pressure or impedance of the affected output channel leg, the power stream will switch to the nonaffected output channel means which presents a lower flow impedance.

As a specific though exemplary operational mode, let it initially be assumed that the power stream issuing from the input channel means 10 has attached to side wall 18 of the interaction chamber means 14, so as to exit via the output receiver channel means 22. If a control signal is applied at the control port means 38 communicating with the output channel means 22, the back pressure and output impedance of the output channel means 22 would thereby be increased affecting the pressure differentials and gradients within the interaction chamber means 14. The power stream would thereafter detach from wall 18 of the interaction chamber means 14, reattach itself to wall 16 of the interaction chamber means 14, and subsequently exit via the output channel means 20 which presents a relatively lower back pressure or impedance.

Since switching operation of the novel fluidic device of the instant invention is contemplated to take place under the sole influence of the respective control port means 36 and 38, it may be necessary to insulate or decouple the novel device from the effects of spurious back pressure caused by loading conditions at load connections 32 and 34, respectively. To this end, the novel invention contemplates the provision of decoupling vents 24 and 26 in the output receiver channels 20 and 22, respectively, downstream of the control port means 36 and 38. Each of the decoupling vents 24 and 26 serves to effectively decouple the respective output receiver channels from the effects of load impedance as above-described. Additionally, the decoupling vents 24 and 26 will be seen to control the steady state output impedance seen by the device and hold such output impedance constant in the following manner.

Specifically, it should be noted that each of the decoupling vents 24 and 26 include restrictions or orifices 28 and 30, respectively, presenting a selective and variable cross-sectional flow area. The area or size of such decoupling nozzles 28 and 30 serve to control the steady state output impedance seen by the device and hold same constant. Additionally, the size of the decoupling nozzles 28 and 30 are contemplated to be utilized so as to control the sensitivity of the fluidic device of the instant invention to the pressure signals applied to the control port means 36 and 38. In this respect, it has been found that a relatively large area decoupling nozzle serves to yield a relatively small back pressure in its associated output receiver channel and thus, a relatively large control signal would have to be applied to the control port means 36 or 38 to generate sufficient back pressure so as to switch the fluidic device. Similarly, if the decoupling nozzle 28 or 30 of the decoupling vents 24 and 26 exhibited a small area, a smaller pressure control signal would be utilized at the control ports 36 and 38 to effect switching of the device.

It has been found that the operational stability of a device having this novel control configuration can be increased though the provision of side vent means 40 and 42 such as depicted in FIGS. 2 and 3. In FIG. 2, the side vent means 40 an and 42 are disclosed as being disposed upstream of the control port means 36 and 38, respectively, and communicating with the output receiver channels 20 and 22, respectively. While stability of the device is increased by such a construction, it has been found that this particular placement of the side vent means 40 and 42 has a tendency to isolate the mechanism from switching back pressure induced by the control signal applied to the control port means 36 and 38. Further, it has been found that if the side vent means 40 and 42 were disposed downstream of the control port means 36 and 38 in the respective output receiver channel means 20 and 22, the control port signal may have a tendency to dissipate into the bleed effected by such side vent means.

So as to overcome these particular operational characteristics, a further embodiment of the novel fluidic device of the instant invention has evolved and is particularly depicted in FIG. 3 of the appended drawings. In the embodiment of FIG. 3, the side vent means 40 and 42 are disposed at the respective control port means 36 and 38 communicating with the respective output channel means 20 and 22, but in such a fashion that a control signal when applied at the respective control port means 36 and 38, serves to effectively block the associated side vent means 40 and 42, respectively. Accordingly, with the embodiment of FIG. 3, for example, the switching operation is assured without the disadvantage of isolation of the device from the back pressure induced by the pressure control signal, and without the disadvantage of bleeding the pressure control signal itself. In effect, the embodiment of FIG. 3 functions as a variable impedance vent. That is, during steady state operation, the vents act as a low impedance to ground. During the switching operation the vent is loaded by the control-signal. This load on the vent causes a load on the output channel which causes the switching of the device as described below.

In operation of the inventive embodiment of FIG. 3, if a control signal were to be applied to the control port means 36, the output channel leg or means 20 of the device would present a high impedance or back pressure to the power jet issuing from the input channel means 10. At the same time, the output channel means 22 would present a relatively lower impedance, this relatively lower impedance being enhanced due to the provision of the side vent means 42. The power stream would thereby switch from output receiver channel means 20 into output receiver channel means 22.

The principles of the instant invention have been found to have applicability in association with interaction chamber means 14 of more or less conventional construction having set back side walls as shown in FIG. 1, as well as with fluid amplifier means having an interaction chamber of the type depicted in FIGS. 2 and 3 which exhibits a diffuser-type construction with two opposite divergent side walls effecting a smooth, continuous, and gradual transition from the throat or nozzle of the input channel means to the output receiver channels 20 and 22. With a construction of interactionchamber such as depicted in FIGS. 2 and 3, the chamber itself defines means for effecting a laminar flow of the power stream along both of the side walls 16 and 18 to a downstream separation point near which the chamber effects an adverse pressure gradient to thereby detach the power stream from one of the side walls so that the power stream exits into one or the other of the output receiver channels provided. This chamber construction may be utilized to advantage in low power, high gain devices and such high gain is attainable without the necessity of utilizing a control port in the area of the interaction region.

A further advantage of the novel construction of the fluidic device can be found in the fact that the inventive construction allows an element designer to interplay the control sensitivity with the back pressure in the manner described hereinabove. Further, it should be recognized by those skilled in the art that while only two output channel legs have been disclosed in association with each fluidic device, a plurality in excess of two output receiver channels could be utilized if so desired. In this respect, it has been found that with the novel construction of FIG. 3, for example, a fan out of about 10 or more can be obtained.

Although the controls have been depicted on the output walls opposite the splitter in the preferred embodiment, such controls could also be placed in the splitter or even in the upper and lower plates. With simple modifications, the construction of OR/NOR gates,

AND/NAND gates, Schmidt Triggers and the like are possible.

It should be understood that the invention is not limited to the exact details of construction shown and described herein for other obvious modifications will occur to persons skilled in the art.

Accordingly, what is claimed is:

l. A back pressure sensitive fluidic device, said device comprising:

an input channel means for issuing a fluidic power stream;

a plurality of output receiver channels for receiving at least a portion of the power stream flow; an interaction chamber means disposed between said input channel means and said output receiver channel means, said interaction chamber means being devoid of control ports and including side walls whereat the power stream attaches to exit into an output receiver channel; control port means communicating with and issuing into said output receiver channels for increasing the back pressure and the impedance of the respective output receiver channel upon application of a pressure control signal thereto, whereby the power stream in said interaction chamber means is selectively switched to another output receiver channel having a relatively lower impedance; and

decoupling vents disposed downstream of said control port means in said output receiver channels to decouple said output receiver channels from the effects of load impedance.

2. A device as defined in claim 1, further including side vent means disposed adjacent said control port means in said output receiver channels for stabilizing the operation of the fluidic device.

3. A device as defined in claim 2, wherein each said decoupling vent includes a decoupling nozzle in said output receiver channel, the flow area of said decoupling nozzle controlling and maintaining substantially constant the output impedance of said receiver channel and thereby controlling the sensitivity of the device to said control signal.

4. A device as defined in claim 3, wherein the interaction chamber means comprises .a diffuser-type chamber having two opposite divergent side walls effecting a smooth, continuous, and gradual transition from the throat of said input channel means to said output receiver channels, said chamber defining means for effecting laminar flow of the power stream along both of said side walls to a downstream separation point, said chamber thereat effecting an adverse pressure gradient to thereby detach the power stream from one of said side walls whereby the power stream exits into an output receiver channel.

5. A back pressure sensitive fluidic device, said device comprising: an input channel means for issuing a fluidic power stream; a plurality of output receiver channels for receiving at least a portion of the power stream flow; an interaction chamber means disposed between said input channel means and said output receiver channel means, said interaction chamber including side walls whereat the power stream attaches to exit into an output receiver channel? control port means communicating with and issuing into said output receiver channels for selectively applying a control signal thereto, said control signal increasing the back pressure and the impedance of the output receiver channel to that a control signal issuing from said control port means serves to block said side vent means; and decoupling vents disposed downstream of said control port means in said output receiver channels to decouple said output receiver channels from the effects of load impedance. 

1. A back pressure sensitive fluidic device, said device comprising: an input channel means for issuing a fluidic power stream; a plurality of output receiver channels for receiving at least a portion of the power stream flow; an interaction chamber means disposed between said input channel means and said output receiver channel means, said interaction chamber means being devoid of control ports and including side walls whereat the power stream attaches to exit into an output receiver channel; control port means communicating with and issuing into said output receiver channels for increasing the back pressure and the impedance of the respective output receiver channel upon application of a pressure control signal thereto, whereby the power stream in said interaction chamber means is selectively switched to another output receiver channel having a relatively lower impedance; and decoupling vents disposed downstream of said control port means in said output receiver channels to decouple said output receiver channels from the effects of load impedance.
 2. A device as defined in claim 1, further including side vent means disposed adjacent said control port means in said output receiver channels for stabilizing the operation of the fluidic device.
 3. A device as defined in claim 2, wherein each said decoupling vent includes a decoupling nozzle in said output receiver channel, the flow area of said decoupling nozzle controlliNg and maintaining substantially constant the output impedance of said receiver channel and thereby controlling the sensitivity of the device to said control signal.
 4. A device as defined in claim 3, wherein the interaction chamber means comprises a diffuser-type chamber having two opposite divergent side walls effecting a smooth, continuous, and gradual transition from the throat of said input channel means to said output receiver channels, said chamber defining means for effecting laminar flow of the power stream along both of said side walls to a downstream separation point, said chamber thereat effecting an adverse pressure gradient to thereby detach the power stream from one of said side walls whereby the power stream exits into an output receiver channel.
 5. A back pressure sensitive fluidic device, said device comprising: an input channel means for issuing a fluidic power stream; a plurality of output receiver channels for receiving at least a portion of the power stream flow; an interaction chamber means disposed between said input channel means and said output receiver channel means, said interaction chamber including side walls whereat the power stream attaches to exit into an output receiver channel; control port means communicating with and issuing into said output receiver channels for selectively applying a control signal thereto, said control signal increasing the back pressure and the impedance of the output receiver channel to which it is applied to selectively switch the power stream in said interaction chamber means to another output receiver channel having a relatively lower impedance; side vent means for stabilizing the operation of the fluidic device, said side vent means being disposed adjacent said control port means slightly downstream thereof and oriented with respect thereto such that a control signal issuing from said control port means serves to block said side vent means; and decoupling vents disposed downstream of said control port means in said output receiver channels to decouple said output receiver channels from the effects of load impedance. 